1. Field of the Invention
This invention relates to an apparatus for etching a semiconductor material such as silicon wafer or glass photomask, and more particularly to an apparatus for etching a film such as an oxide film to be treated, applied on one of the surfaces of a semiconductor material.
2. Description of the Prior Art
In manufacture of semiconductor circuits, an oxide film is formed on one of the surfaces of a semiconductor material such as a silicon wafer, and then etching of such an oxide film is carried out in order to permeate diffusion material of P-type or N-type selectively on said one surface. For this purpose, photosensitive liquid (photo-hardening type photoresist) is coated on a thin film condition on predetermined portions of the wafer surface, and is next printed thereon and developed for forming a pattern for etching of oxide film, said pattern providing semiconductor circuits as a semiconductor device.
An apparatus for the above described etching has been known, in which a cup-shaped basin is used for etching a film to be treated, applied on one of the surfaces of a semiconductor material which is supported by a rotatable chuck, spaced above the top portion of the basin, with one surface facing downwardly. The etching of a film applied on one wafer surface is accomplished by introducing an etchant through a passage formed in a lower part of the basin and blowing the etchant upwardly against the one surface of a semiconductor material. An end point of the etching has been determined in accordance with a lapse of a predetermined time.
An end point of the etching should be correctly determined. However, the above described conventional method does not necessarily provide a correct discrimination of an end point of the etching, which results in an over-etching such as "side-etch" or "under-cut", or results in an insufficiency of etching.